Hafler DH101 preamp repair and mods?

Tried and tested Sulzer-Borbely Regulator Power supply, results are more than good no hum or noise perfectly stable, but I returned the original transformer is much more pleasant to listen to.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.

Hi, Really great work, love the power supply, whats that other small PCB in power supply section. What does pre-amp sound like now, do you use your pre-amp to play a lot of LP's.
 
Was that power supply board a home made board, or did you purchase it?



To answer your question ouimetnick, PCB I've made ​​and constructed according to the appropriate size so that it can be placed into the housing HAFLER DH-101, I also listed several changes in the form of improved power supply. If anyone is interested I can send you the file and you can easily make (toner transfer) method. I just can say the power supply is working great and is very quiet. My HAFLER DH-200 power amplifier came from Ebay and I begin modifications on them, expecting some parts from Ebay (Power Supply cap, Power Switch, Polypropylene capacitor set ... etc.) for now replaced several components and is fully wired with "Van Den Hull CS18" wire and I can say sounds awesome.
 
Hi, Really great work, love the power supply, whats that other small PCB in power supply section. What does pre-amp sound like now, do you use your pre-amp to play a lot of LP's.

Hi Wally5 thank you, I finally found some time to answer some questions because it is difficult to align the time together with children, wife and job. If you are able to notice in the pictures I took out preamp coupling capacitors of 10uF because the CD player already have Black Gate capacitors at the entrance HAFLER DH-200 also so there is no need for them because they degrade the signal. All transistors are hfe matched so that the dc output to around 3-5mV and that is more than good. Results are immediately, wide stage, dynamics, and of course the magic hidden details, simply to try and see the difference. Even John Hillig of Musical Concept in his super mode HAFLER DH 101 recommend removing input capacitors from preamp, all that matters is that you are sure that the power amplifier input coupling capacitor exist.
 
DH-101 Grounding mod from Audio Amateur years ago

Attached is the grounding mod for the DH-101 published in Audio Amateur many years ago. Somebody asked about it earlier and I don't think I ever saw it. My apologies if this has been put up elsewhere.
 

Attachments

  • DH101 grounding mod.gif
    DH101 grounding mod.gif
    12.7 KB · Views: 596
Hafler DH 101 preamplifire rebuild

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
hafler pcb

Made a new plexiglass carriers for the Gold-plated RCA connectors, the new quality PCB board, the wiring will be Van Den Hul CS-18, mains filter and torus transformer will be installed. After the completion of the modification will put new pictures.




An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
is possible to buy a pcb like these, because the original pcb died, thanks.
 
Just beginning my own upgrade and choosing materials. Is the Van Den Hul CS-18 wire you chose a shielded wire? I know the company recommends it for use in preamp circuitry, but the product description did not mention shielding, and several people recommended shielded wiring as part of an upgrade. On the same topic, the wire connecting all RCA jacks has no insulation (neither did the orginal) - why is that OK?
 
It has been many years since I have had a Hafler DH-101 but I picked up a unit off Ebay for under 60.00 last month 12/2013. The unit appeared stock. The unit sounded good and was quiet with no hum or noise when it arrived. The first change that I made was to the power supply. I used Panasonic 2200uf 35v for (C24, C25) and 1000uf 25v replacing (C26,C27) capacitors. I did not bypass these caps with .1uf film as others have done. The power supply upgrades made the biggest changes to the sound. More bass and larger more focused sound stage. The change that made the next biggest change was capacitor C20. The stock value is 10UF bipolar. I tried everything from a Nichon Muse ES series 10UF , various film caps to a bare wire. Did not like the muse and replaced C20 with a bare wire. When I wanted to test different film caps I connected them between the output RCA jack hot terminal and the wire that was attached to RCA jack. That way I did not have to solder and un solder against the circuit traces to test what the final value should be for C20. I found the bare wire to be very nice at low volume and very reveling but as the volume increased the sound became too much of a good thing. C11 and C17 also got replaced by Nichicon MUSE ES series with the same values listed in manual. No complaints and happy with those capacitors. I replaced some of the tone capacitors with what ever was around the house. Not much of a difference if at all. When I use the unit I am bypassing the tone controls via the switch provided on the preamp so did not put much into that area.
If I was to do it all again first I would do the power supply first. Then I would do any other upgrades except C20. I would replace C20 with a bare wire and experiment with different capacitors attached to the hot lead on the output wire of RCA jack and the with that was attached to the saving C20 for last as your final voicing of the preamp. Have fun.
I am not using the phono section so no changes were made there.
 
Just beginning my own upgrade and choosing materials. Is the Van Den Hul CS-18 wire you chose a shielded wire? I know the company recommends it for use in preamp circuitry, but the product description did not mention shielding, and several people recommended shielded wiring as part of an upgrade. On the same topic, the wire connecting all RCA jacks has no insulation (neither did the orginal) - why is that OK?

John Hilling from Musical Concept once said that the twisted wire in the signal path sounds better than a shielded cable, I have to honestly say that I've tried both, and for me there is no difference because it is too short a path of RCA connectors to PCB.
 
Stranded phone wire. Won't break. You can twist away. Nothing better needed inside a chassis.

I built a 101 when they first came out. Maybe I did a little better lead dress, but it worked great. I never had second sources power up, so input crosstalk was not an issue. I did the factory phono upgrade. Before the switches went bad ( really cheap remember) I was talked into swapping it for a "High end" preamp. An Amp Holman. What a POS. Went for a Hafler 110 I still have. Pots need replacing, but sonically a match for my Nac CA-5 I still use. Any better than a couple of modern op-amps with good power supply? Well, maybe not. Still. they have nothing to hide.
 
My DH-101 is due for a re-cap, as I've owned it since 1982. I know I have one dicey cap in the power supply, so my first step is to redo all four of those. I have heard that added capacitance makes a nice improvement (as kevin99705 has done above), so that is how I had planned on going with the power supply.

As for the other caps, I realize I can buy a kit on eBay that has a full set of the caps for PC-4, but I am not sure if those are of sufficient quality. Or, might I be better off sourcing my own?

Hafler DH 101 PC 4 Capacitor Upgrade Kit | eBay

The reason I am thinking of doing this now is that I'm hearing some odd phono input distortion, which seemed to happen only in the last month or so. I thought it might be mistracking, but I dug out my DH-110 to play the turntable through and I don't think I'm hearing it (via headphones). I am still swapping components around to eliminate the problem, so the jury's still out on the true source. But the DH-101 needs the new caps anyway.

Finally, many of the links and photos earlier in this thread are pretty much dead now. Is there a newer/better source for me to look at some of the Audio Amateur modifications? I have always liked how this preamp sounded and in fact, I like it better than the used DH-110 I picked up about 15 years ago.
 
Administrator
Joined 2004
Paid Member
Hi Wildcat,
I've rebuilt many and also have boosted their performance. I wouldn't touch a kit (I did look at it, auction ended but still examined it) as you aren't going to get what you need.

Be aware that what you mostly read up on this is a lot of misinformation and stuff that is just plain wrong. The capacitors will improve the sound quality - iff (double f intended) there are capacitors with problems. Log onto Digikey or Mouser and buy good quality stuff. It'll be cheaper and faster than doing the Ebay thing anyway.

Do not greatly increase the capacitance of the main filter capacitors. Buy good quality ones the same (or slightly higher capacitance if you must). Larger capacitors do not increase bass or lower distortion. Expectation bias is at work here. The larger values bring with them some negatives which you don't need. The capacitors were not undersized.

Big improvement #2 is to match the input diff pair, and the drivers. There are also a lot of other things you can do, and you will know this if you are familiar with working on amplifiers. They can sound a lot better than they did when new. If you aren't familiar and comfortable working on these, refer the work to a good technician.

What is the most expensive component in most products?

The circuit board. Do not damage the traces! You're further ahead destroying a bad part than lifting traces if it is difficult to remove.

I have had to repair many boards with damage due to previous people working on them. The board will determine if the amp is reliable or not in the future.

Best of luck with your repair. Try and use higher voltage capacitors that fit the board. Never use a part that is too large.

-Chris
 
Hey @anatech--congrats on the Canadian girls' hockey team at the Olympics--great game! :D (Hate to say it but I was rooting for Canada anyway--they're our southern neighbors, from where I'm sitting. ;) )

I think a reply was removed overnight (possibly spam). My post was from 2014, and I've been using a Conrad-Johnson preamp for a few years now. ;) It was one of those deals I couldn't pass up. I've retired the ol' 101, but since I built it originally, I'm still hanging onto it for future use.

Agreed, though, on your thoughts. I read of some DIYers trying to re-engineer components, or even professional techs who think they can "improve" on what the designers originally intended. C-J components are a good example, in fact. Buying a used preamp or amp requires reading the descriptions carefully. If it was returned to C-J for a touch-up or new capacitors, it's all good. But I also read some ads where an owner who has sent it out to a tech who felt things could be "improved"...no thanks. It not only could have dubious benefits, it also harms the resale value. And if it ever has to go back to C-J...well, to paraphrase their own words, they've seen some unbelievable things done to their components over the years, and have to charge extra to undo that damage before they can work on it properly.

It's not as drastic as those old Hafler "upgrades" where the companies completely replaced all the circuit boards with their own--that made no sense, as you only had a Hafler "box" connected to completely different circuitry. You no longer owned a Hafler, in other words. I forget the names, but there were a couple of companies who did that back in the 80s.